Effects of endodontic instrument handle diameter on electromyographic activity of forearm and hand muscles

Aim To determine the influence oft-he handle diameter of endodontic instrum ents on forearm and hand muscle activity using electromyographic (EMG) reco rding. Methodology Size 45 K-type files were fitted with four different handle dia meters; 3.5, 4.0, 5.0, and 6.0 mm. Seven dentists then attempted to negotia te to the working length acrylic resin root canals with each of the four ha ndle sizes using a reaming motion. EMG activities were recorded from the fl exor pollicis brevis muscle (f.p.b.), the flexor carpi radialis muscle (f.c .r.), and the brachioradialis muscle (b) with bipolar surface electrodes. T he time taken to negotiate the canals, the area of integrated EMG that corr esponded to the amount of EMG activity required during penetration and the maximum amplitude of EMG were measured using the EMG data. Results were analysed statistically using a one-way factorial ANOVA test an d multiple comparison tests. Results Reaming time and integrated EMG area o f each muscle decreased with an increase in handle diameter. The most signi ficant difference in time and area of integrated EMG was detected between h andles of 6 mm and 3.5 mm diameter (time: P < 0.01, area of the f.p.b.: P < 0.01, area of the f.c.r. and b: P < 0.05), and between handles of 5 mm and 3.5 mm diameter (P < 0.05). Both 5 mm and 6 mm handles significantly decre ased the maximum amplitude of EMG recorded from the f.p.b. compared with 3. 5 mm handles (between 3.5 mm and 6 mm: P < 0.01, between 3.5 mm and 5 mm: P < 0.05), Conclusion The results indicate that handle diameter has an effect on reami ng time as well as on muscle activity. As a consequence, handle diameter in fluenced operator performance during instrumentation.